The Artificial Intelligence of GTA: Vice City

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What makes them tick? We take a deeper look into the denizen of Vice City.

By Douglass C. Perry

A million things comprise the making of a videogame. Coders are constantly altering and tightening physics, fixing cameras, tweaking difficulty levels and experimenting with artificial intelligence. It's not like programming on your TRS 80 anymore. The PS2 itself has a triple thick manual that takes weeks to get through.

And so, when a massive multifaceted game such as Grand Theft Auto III comes along, you can bet your Floridian print shirt that the good folks at Rockstar North are working overtime seven days a week to make every spec of the game work and well. Will Grand Theft Auto: Vice City supercede its predecessor? As we explore the various parts of Rockstar North's fifth iteration in the series, we must take a hard look at the game's ambient, civilian life.

Like Liberty City before it, Vice City is populated by hundreds of "people" going about their lives: They may be walking the streets, but they're actually on their way to do something. They're all programmed, so to speak, like we are in our daily working week, to do something. The roller skaters roller skate, the drivers drive, and the business people look...busy.

But what else are they doing? Are they just robots with bikinis? Or agro-gang members that simply react to your presence? And, more importantly, do they react to you, and with what complexity? We spoke with Dan Houser, VP of creative, and Rockstar North's James Worrall who gave us an inside look at the artificial intelligence behind the denizens of Vice City.

IGNPS2: Can you tell us some of your favorite new additions to the walking life in Vice City?

Dan Houser: We set out with the goal of giving the ambient city life a lot more personality - with more variety in the way pedestrians look, more variety in the behavior, what they say and when they speak and more for the player to interact with. The new police behavior I love - they do more and are more likely to surprise the player. Also some of the 1980s characters hanging out in the map are great to interact with, be it the waspy snobs on the golf course or the degenerate street gangs hanging out in the ghetto.

James Worrall: The roller skaters are pretty cool and you¿ll see cigar girls walking Ocean Drive. My favorite is the improved the gang AI. Now you¿ll see them hanging out in gangs on street corners and if you stand close by and eavesdrop you can hear some great comments and conversations.

IGNPS2: I heard about pizza delivery mission in Vice City. Are there actual pizza parlors?

James: Pizza parlors, and more; The Player will find these particularly useful and each is staffed by a loyal McJobber that will serve the Player through thick and thin - even if he has to do so ducked behind the counter whilst bullets ricochet around him!

IGNPS2: We know there is a roller skater, what other activities do pedestrians do in Vice City?

James: They cruise on leisure boats, take the bus around town, hail taxis, jack cars, and ask if you know anything about toilets¿.

Dan: They also mug people, go to nightclubs, get into fights, crash cars and bikes, run businesses, shop, eat, dance, discuss politics and abuse one another. The usual sort of city life. We have tried to add as much variety to people's behavior as possible while still keeping the AI manageable given the number of different scenarios we can think up in a city. We're trying to combine the look of the character with their behavior¿are they aggressive or scared, busy or hanging about¿with what they are saying and what their voice sounds like to make the ambient characters in the city feel as varied and alive as possible.

IGNPS2: In Grand Theft Auto 3 you had different districts and each district had its own pedestrians. Will there be more in this one? How do the inhabitants differ as you travel around?

Dan: Of course. That's the trick in bringing a city to life. A city like Vice City has some very glamorous districts, especially on the ocean and some dodgy districts where more unsavory characters hang out. Gangs have control of sections of the city; shoppers prefer the mall; fat people enjoy the food court. That sort of thing.

IGNPS2: What's the weather like in Vice City? How do pedestrians react to weather changes?

The AI in Vice City is more complex this time around. Though this guy is a few bits short...

Dan: It's down south, so usually the weather is pretty good - we really wanted to capture the sunny, almost cooked vibe that you see down there, especially after spending so long in murky and dirty Liberty City. Aaron and the whole Rockstar North art team did a brilliant job in giving Vice City a different look to Liberty City- the game world just feels hot and sun bleached. The AI, vibe and personality of the city's inhabitants and visitors have been set to match. People want sun and expect it, but when they don't get it, they are very angry. Vice City is a city full of tourists and of people who moved there to get away from the rest of America.

James: When we were over in Miami there was a hurricane lurking off the coast, and whenever it rained the streets became deserted. It amazed us because it always rains in Scotland and quite often we¿d find we were the only people on Ocean Drive! So when it rains in Vice City you¿ll find pedestrians running for cover and the streets becoming quite lonely. Cars drive more slowly to cope with the slippery roads and rain splashes off the ¿camera¿, running to the edges of the screen if you¿re traveling at speed. But when the sun comes back out again the beaches start to fill with sunbathers and the sun glints off the beautiful turquoise sea. Cars have spectacular flares, the hot blacktop creates a heat haze and while driving down a boulevard the sun flashes through the palm trees.